256 



Dr. C. Todd and Mr. E. G. White. [July 1, 



times. The serum so treated was now found to be completely " exhausted " 

 for the corpuscles of A, that is to say, in the presence of fresh guinea-pig 

 serum it showed no trace of haemolysis with the corpuscles of A, but remained 

 powerfully hsemolytic for those of B. 



Another lot of serum was similarly treated with the corpuscles of B, and 

 in this way a serum was obtained which was " exhausted " for the corpuscles 

 of B but remained powerfully hsemolytic for those of A. 



The two exhausted sera so prepared now constituted specific reagents for 

 the corpuscles in question, and by means of these reagents it was possible to 

 analyse a mixture of the two corpuscles by dissolving out at will either of 

 the corpuscles with the corresponding serum. 



The exhausted sera having been prepared and tested, the animals were 

 each bled from the jugular vein into graduated vessels containing a known 

 volume of a 4-per-cent. solution of sodium citrate, from 2 to 4 litres of 

 blood being taken from each animal. The citrated blood from each animal 

 was then transfused into the jugular vein of the other, the whole process being- 

 carried out as quickly as possible and the blood being kept at body temperature. 



After an interval of about a quarter of an hour, to ensure a uniform 

 distribution of the injected blood in the circulation, a sample was taken from 

 each animal and allowed to run into citrate to prevent clotting. Similar 

 samples were taken daily throughout the experiment. 



The examination of these samples was carried out thus : 



A 2-5-per-cent. suspension of the sample blood was made in normal saline. 

 This was centrifuged to get rid of serum and the corpuscles resuspended in 

 saline. This suspension was then tested by being mixed with equal volumes 

 of the exhausted serum and a 1/10 dilution of fresh guinea-pig serum. 



The test was put up as follows : — 



In this tube the corpuscles of B are picked out and hamiolysed : those of A 

 remaining unchanged. 



Here the corpuscles of A are dissolved, those of B remaining unchanged. 

 3. 2 - 5-per-cent. suspension of red blood corpuscles ... - 5 c.c. 



1. 2-5-per-cent. suspension of red blood corpuscles ... 



Serum exhausted with corpuscles of Bull A 



1/10 dilution of fresh guinea-pig serum 



2. 2'5-per-cent. suspension of red blood corpuscles . . . 



Serum exhausted with corpuscles of Bull B 



1/10 dilution of fresh guinea-pig serum 



Normal saline 



Here both corpuscles are present, giving the total. 



1-0 



